Steve;
My Scott pinfire reads on the top rib from breech toward muzzle;

W&C Scott & Son 7 Dorset Place, Pall Mall East, London For Benj D Kennedy, Louisville KY

Each lock plate reads W&C Scott & Son, locks are bar action.
Proof marks are London of the 1855-1868 type.
IF for a cylinder bored gun (which this one is) & given the provisional plus definitive proofs rather than the combined proof the marks could have stayed the same up till 1887.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra